https://www.acs.org/climatescience/atmosphericwarming.html has a pretty good (though above ELI5) set of graphs and explanations of the chemistry involved.
https://history.aip.org/climate/co2.htm
> "Improved physics theory and precise laboratory measurements in the 1940s and after encouraged a new way of looking at the absorption. Scientists were especially struck to find that at low pressure and temperature, each band resolved into a cluster of sharply defined lines, like a picket fence, with gaps between the lines where radiation would get through.(24) As Hulburt and Callendar had claimed, the most important CO2 absorption lines did not lie exactly on top of water vapor lines. Instead of two overlapping bands, there were two sets of narrow lines with spaces for radiation to slip through. So even if water vapor in the lower layers of the atmosphere did entirely block any radiation that could have been absorbed by CO2, that would not keep the gas from making a difference in the rarified and frigid upper layers."
However, this CO2 at 12km only accounts for about 1/3 of the warming - what happens is that the warming is amplified by more evaporation (due to increased warmth) which injects more water vapor into the atmosphere (from the oceans and land evaportation) and that's the other 2/3 of the effect more or less.
It is a slow change, but steady. It's entirely possible that humans will be able to adapt to much of the change, assuming we stop pumping fossil CO2 into the atmosphere within the next few decades or so.
Both the concentration and effect of CO2 are small but since human life has a limited temperature band, even a 1.5°C increase does matter.
And so far I have just been applying some commonsense to your number comparison logic. I didn't even have to understand the basic mechanisms of how it works, just that there might be some effect.
CO2 is the point of concern because the carbon cycle is slow. Any CO2 we add will be there for many decades. So it’s like compound interest: a small change over time adds up to a noticeable effect.
The water cycle is very short, extra water vapor rains out quickly.
This explains the physics:
Many centuries.
Imagine you have a surface that reflected a unit X of heat back to its source. Now it does 2X. In the next few decades it’s going to do 3X.
Does it make sense now? That X was enough to keep us warm. Now we’re facing with that amount increasing significantly.
The reason CO2 is like very spicy pepper is that it is very good at absorbing infrared radiation from the sun, and then re-emitting that energy as heat in the atmosphere.
https://news.climate.columbia.edu/2021/02/25/carbon-dioxide-...
If cheap clean portable fusion was invented tomorrow, if would quickly be banned for one reason or another. People need to sell disasters, not solutions.